video of Copper-bellied Water Snake, filmed in Muscatatuck National Wildlife Refuge, Indiana, USA

Adults are 24–40 inches (76–122 cm) in total length, and can reach up to 55 inches in some states such as Kansas.

It gets its common name because it has no patterning on its underside. Subspecies can vary in color from brown, to gray, to olive green, with dark-colored blotching down the back, and an underside that is yellow, brown, red, or green.